The present invention generally relates to supramolecular assemblies, and their modes of synthesis.
Design principles that are based upon the concepts of crystal engineering and self-assembly have recently afforded new classes of crystalline solids that possess important physical properties such as bulk magnetism or porosity. Large-scale molecular networks have been developed to encapsulate other materials and these are playing an ever-increasing role in the pharmaceutical industry and as materials for sensors, and liquid crystals. In addition, with the inclusion of metals within the structures, the large polymers formed by these crystals can possess, among other properties, catalytic, fluorescent, and magnetic attributes.
The molecular/supermolecular building block (MBB/SBB) approach has recently emerged as a powerful strategy for the design and construction of solid-state materials. This is evidenced by the burgeoning academic and industrial interest in the class of materials known as metal-organic frameworks (MOFs), for which desired functionality can be introduced at the molecular level prior to the assembly process. See, e.g., Stein et al., Science 1993, 259, 1558-1564; Férey, G., J. Solid State Chem. 2000, 152, 37-48; Eddaoudi et al., Science 2002, 295, 469-472; Kitagawa et al., Angew. Chem. Int. Ed. 2004, 43, 2334-2375; Moulton et al., Chem. Rev. 2001, 101, 1629-1658; Eddaoudi et al., Acc. Chem. Res. 2001, 34, 319-330; and U.S. Pat. No. 6,624,318 (hereby incorporated by reference herein in its entirety).
Assembly of finite supramolecular polyhedra and periodic extended networks from MBBs and SBBs offers great potential for the rational design and synthesis of functional materials and nanostructures. Cheetham et al., Angew. Chem., Int. Ed. 1999, 38, 3268-3292; Yaghi et al., Nature 2003, 423, 705-714; Seo et al., Nature 2000, 404, 982-986; and Desiraju et al., Nature 2001, 412, 397-400. This approach has been explored and, to some extent, has proven to be successful in metal-ligand directed assembly. See, e.g., Moulton et al., supra; Hoskins et al., J. Am. Chem. Soc. 1990, 112, 1546-1554; Seidel et al., Acc. Chem. Res. 2002, 35, 972-983; Takeda et al., Nature 1999, 398, 794-796; Kitagawa et al., supra; Eddaoudi et al., supra; Caulder et al., Acc. Chem. Res. 1999, 32, 975-982; Yaghi et al., supra. Metal-carboxylate based clusters, where metals are locked into their positions, have been synthesized in situ and successfully used as rigid directional secondary building units (SBUs) to design and construct stable open metal organic assemblies that maintain their structural integrity even upon complete removal of their guest molecules. See Li et al., Nature 1999, 402, 276-279; Chui et al., Science 1999, 283, 1148-1150, Yaghi et al., supra; and Yaghi et al., J. Solid State Chem. 2000, 152, 1-2.
Conventional MBBs and SBBs (coordination clusters or organic ligands) with varied connectivity and specific geometry and directionality are readily accessible, and can be employed to access structures where the MBBs and SBBs augment the vertices of a given net. See Ockwig et al., Acc. Chem. Res. 2005, 38, 176-182; Liu et al., J. Am. Chem. Soc. 2005, 127, 7266-7267; Brant et al., J. Mol. Struct. 2006, 796, 160-164; and Liu et al., Chem. Commun. 2006, 14, 1488-1490. Nevertheless, it is an ongoing challenge to absolutely predict the network topology of the constructed MOF. Accordingly, the ability to target nets that are exclusive for a combination of building blocks presents greater potential towards prediction, design, and synthesis of the resultant framework in crystal chemistry, and with a high degree of control over structure and functionality.